“Danke” is appropriate to use in most situations, however if you want to add a bit of politeness you could say “Danke schön” or if you wanted to express how thankful you are you can say “Vielen Dank” (some people also say “vielen vielen Dank” when they are very happy about something and want to emphasise that, for example if you win an Oscar you might say “Vielen vielen vielen Dank!”).😁